November 28, 2010 -- CHICAGO - Increased use of preoperative breast MRI does not raise the overall mastectomy rate, according to researchers from the University of Genoa in Italy -- good news as the modality comes under scrutiny as a tool for diagnosing and managing breast cancer in high-risk populations.

In a Sunday session at the RSNA meeting, Fabio Chiesa, MD, presented a study he conducted with colleagues that evaluated preoperative breast MRI's overall effect on mastectomy rates. The study included data from 1,522 breast surgical procedures performed from January 2003 to December 2008 at San Martino Hospital in Genoa. Of these procedures, 983 were clinically indicated due to removal of a needle-biopsy proven cancer.

During the study time frame, the team found that the mastectomy rate for the total number of performed surgical treatments remained less than 22%. The rates for each year are as follows:

2003 -- 20.7%

2004 -- 15.7%

2005 -- 15.7%

2006 -- 13%

2007 -- 14.3%

2008 -- 21.4%

The overall rate for the entire period was an average of 17.1% (168 mastectomies out of 983 surgical procedures).

This occurred despite the fact that the use of preoperative breast MRI increased dramatically over the study period, Chiesa said. Of the 105 women who underwent preoperative breast MRI exams, three were performed in 2003, two in 2004, 13 in 2005, 14 in 2006, 31 in 2007, and 42 in 2008.

The rate of mastectomy was higher among these women who had preoperative breast MRI, Chiesa told session attendees: 37.1% of these women had mastectomies, compared with 14.6% of those whose surgeries were staged without MRI.

Why the higher mastectomy rate for the patients in the preoperative MRI group? Because the procedure is preferred in patients with higher suspicion of extensive disease at clinical exam and conventional imaging -- i.e., mammography and ultrasound -- according to Chiesa.

"The higher mastectomy rate in patients staged with MRI at our institution could be ascribed to strong selection bias, due to our nonroutine use of breast MRI," he said.

Preop breast MRI means fewer surgeries

In a related study presented during the same session, researchers at Memorial Sloan-Kettering in New York City found that women with early-stage breast cancer who underwent preoperative breast MRI, compared to those who did not, were more likely to have extremely dense breasts (28% versus 6%) and mammographically occult cancer (24% versus 9%). But the group also found that preoperative breast MRI actually decreased the total number of surgical procedures performed in women with early-stage breast cancer who were undergoing breast conservation therapy (BCT) and radiation therapy (RT).

Jie Li, MD, and colleagues reviewed 1,224 staging breast MRI exam records taken between 2000 and 2004. Among these, 174 staging MRI exams were performed in women with American Joint Committee on Cancer (AJCC) 0, I, or II cancer -- diagnosed by biopsy -- who were undergoing breast conservation therapy and radiation therapy. A control group of 174 women who were also undergoing BCT and RT but who did not have MRI staging was also included.

The cohort of women that had preoperative breast MRI had fewer total operations following initial diagnosis compared to the cohort that did not, Li said: 227 compared to 252, respectively.

"Preoperative staging MRI decreased the total number of surgical procedures in women with early-stage breast cancer undergoing BCT and RT," she told session attendees.